Adds initial JNI bridge code for Background Scheduler implementation.

components/offline_pages/background/scheduler.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_OFFLINE_PAGES_BACKGROUND_SCHEDULER_H_
 #define COMPONENTS_OFFLINE_PAGES_BACKGROUND_SCHEDULER_H_
 
 namespace offline_pages {
 
 // Interface of a class responsible for scheduling a task to initiate
 // processing of background offlining requests upon select system conditions
 // (such as having a network connection).
 class Scheduler {
  public:
   // Defines a set of system conditions to trigger background processing.
   struct TriggerCondition {
     // TODO(dougarnett): define network, battery, power conditions.
   };
 
   Scheduler() {}
   virtual ~Scheduler() {}
 
-  // Ensures that the system has a task scheduled for |trigger_conditions|.
+  // Schedules the triggering of a task subject to |trigger_conditions|.
   // This may overwrite any previous scheduled task with a new one for
-  // these conditions.
-  virtual void EnsureScheduled(const TriggerCondition& trigger_condition) = 0;
+  // these conditions. That is, only one set of triggering conditions
+  // is scheduled at a time.
+  virtual void Schedule(const TriggerCondition& trigger_condition) = 0;
 
-  // Clears the currently scheduled task, if any.
-  virtual void ClearScheduled() = 0;
+  // Unschedules the currently scheduled task, if any.
+  virtual void Unschedule() = 0;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_BACKGROUND_SCHEDULER_H_